Fatigue Analysis of a Motorcycle Frame System Based on a Road Test and the Finite Element Method

A motorcycle frame system is a load bearing structure that always appears to suffer fatigue damage after running for a long time, indeed the fatigue life of the frame ultimately decides the service life of a motorcycle. In our work, we predicted the fatigue life of a motorcycle frame manufactured from two different materials by carrying out a road test in combination with computational simulation work based on the finite element analysis method. Firstly, signals from the strain and acceleration stemming from the key parts of the frame were collected by the road test, from which we have a preliminary understanding of the amount and distribution of stress. After this a finite element model and a multi-body dynamic model of the frame were built to obtain the results of the stress and information on the load based on the road test. According to the different material properties of Q235 and AZ91, we finally obtained the fatigue life and also discovered the weak parts of the frame. From the road test and results of the simulation we concluded that at 50km/h, most of the stresses inherent in the Q235 frame were well under the yield strength of the material. Indeed the high stress that results in a short fatigue life in some places was caused by concentrated stress and some unreasonable structural design. The stress of the AZ91 fame was the same as the Q235 in the experimental working conditions, while the weight of the frame can be reduced significantly. However the damage caused by fatigue that appeared earlier in the AZ91 frame than the Q235 frame can be attributed to its lower strength material.